activity is completed, the area should be restored to its original state 

 by removal of spoil banks and other construction debris that will adversely 

 affect environmental quality. 



Even with the best safeguards, temporary adverse effects can result 

 from construction activities. Therefore, it will often be necessary to 

 avoid work during particularly critical periods of migration, breeding, 

 feeding, and other functions of aquatic life. 



Operations : Effects related to the day-to-day use and maintenance 

 of roadways are usually of lesser impact but can be significant in certain 

 situations. Continuing disturbances occur because of altered runoff from 

 road surfaces, soil erosion, and the introduction of salts, herbicides, 

 and street surface contaminants into nearby watercourses. 



4.8.4 Causeways 



Solid-fill causeways have the potential for a number of adverse 

 environmental effects including degraded marshes and choked-off bays and 

 tidal tributaries. Any type of solid-fill causeway can disrupt the natural 

 tidal flow in an estuary sufficiently to upset the delicate salinity balance 

 essential for the survival of many estuarine organisms. Besides obstruct- 

 ing tidal flushing, causeways also act as water barriers during severe 

 storms and hurricanes. For example, a water pileup behind the causeway in 

 the late 1960's killed all of the ground-nesting birds in the Pelican Island 

 National Wildlife Refuge [79]. 



Location and Design: The construction of a number of highways through 

 marsh areas has effectively separated the upper reach of a tributary system 

 of a wetland from the lower reach, completely altering the circulation 

 patterns of the entire marsh system. The blockage has prevented the normal 

 circulation of waters and exchange of nutrients and organisms and lowered 

 the productivity of the coastal system [80]. The effects of such "dams" 

 could be minimized if pilings and piers had been used for construction 

 instead of solid-fill causeways. The basic circulation pattern of the 

 tributary wetlands or streams may be preserved by appropriate use of 

 culverts under filled causeways. 



Solid-fill construction usually requires extensive dredging for fill 

 and the excavation of construction canals, which result in additional 

 loss of wetlands and tidelands, soil discharge into the estuary, disruption 

 of water flows, and mud waves. 



The extensive use of construction channels for barge access to 

 construction sites has changed water flow patterns, even when the completed 

 highway is elevated on pilings. Such channels are usually perpendicular 

 to water flow and become repositories for silts, sediments, and organic 

 pollutants. The resultant conditions produce many of the adverse effects 

 of stagnant holes and dead-end canals. 



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